Lithium niobate tuning fork-enhanced photoacoustic spectroscopy and light-induced thermoelastic spectroscopy

In this paper, the performance of two self-designed lithium niobate tuning forks (LiNTF), round-head and tapered LiNTFs, was systematically explored in lithium niobate-enhanced photoacoustic spectroscopy (LiNPAS) and light-induced thermoelastic spectroscopy (LITES) sensors. Finite element analysis results revealed that the stress and surface charge density of the LiNTFs were higher than those of the standard quartz tuning fork (QTF), owing to the high piezoelectric coefficient and electromechanical coupling coefficient of the LiNbO3. The sensing performance of the two LiNTFs was experimentally evaluated, and acetylene (C2H2) was used as the test gas for performance validation. In the C2H2–LiNPAS system, the 2f signal peak values of the round-head LiNTF and the tapered LiNTF were 3.47 times and 4.29 times higher than those of the standard QTF, respectively. When the average time reached 1000 s, the minimum detection limits (MDLs) of the sensor based on round-head LiNTF and the tapered LiNTF were 723 and 450 ppb, respectively. In the C2H2–LITES system, the 2f signal peak values of the round-head LiNTF and the tapered LiNTF were found to be 3.79 times and 5.13 times higher than that of the standard QTF. The MDLs of the LITES sensor based on the round-head LiNTF and the tapered LiNTF were determined to be 101 and 52 ppb, respectively.